Mission success! NASA confirms DART changed the direction of asteroid Dimorphos

The results are in: DART, the mission to change the path of an asteroid, has successfully achieved its objective and moved a stadium-sized space rock further than NASA originally expected.

On 27 September, the Double Asteroid Redirection Test (DART) spacecraft was deliberately smashed into the surface of the asteroid Dimorphos at more than 23,000 km/h after an 11-million-kilometre journey.

It was part of a mission by NASA and the Applied Physics Laboratory at John Hopkins University to see whether human intervention could alter the trajectory of a space objects—such as an asteroid—in case the need to protect Earth from a catastrophic collision arises in the future.

Now, NASA has confirmed the orbit of the target asteroid has been changed by the high-speed impact, marking the successful completion of the project started back in 2017.

What do we know after DART’s crash into Dimorphos?

How do we know it worked?

The US$330 million spacecraft’s impact was only expected to shift the position of Dimorphos by one millimetre, but in the scheme of its 11-hour, 55-minute orbit around the nearby asteroid Didymos, even this miniscule shift could shave over a minute from its space loop.

The last complete image of asteroid moonlet dimorphos, taken by the draco imager on nasa's dart mission
The last complete image of asteroid moonlet Dimorphos, taken by the DRACO imager on NASA’s DART mission from ~7 miles (12 kilometers) from the asteroid and 2 seconds before impact. / Credit: NASA/Johns Hopkins APL

Prior to the impact, the mission team finalised its calculations of Dimorphos’ orbit by measuring the eclipses between the 160-metre asteroid around its 780-metre parent – each dip of light as one passes in front of the other providing calibration intervals for scientists on Earth.

That process, was repeated in the aftermath of the collision using powerful telescopes at Lowell Observatory in Arizona and the Twin Magellan Telescopes in Chile.

These calculations found a whopping 32-minute change in Dimorphos’ orbit time – 25 times greater than the mission’s 73-second benchmark.

“This result is one important step toward understanding the full effect of DART’s impact with its target asteroid” says NASA Planetary Science Division director Lori Glaze.

“As new data come in each day, astronomers will be able to better assess whether, and how, a mission like DART could be used in the future to help protect Earth from a collision with an asteroid if we ever discover one headed our way.”

What’s next for the DART mission?

While the successful change in Dimorphos’ orbit has been confirmed, the DART mission team is continuing its analysis of the impact’s aftermath.

Initial pictures captured by the Hubble Space Telescope in the first 22 hours after the impact showed the ejecta—the eruption of asteroid debris from the point-of-impact—substantially extending as light rays from the main body.

Images from southern astrophysical research (soar) telescope showing dimorphos and dart spacecraft impact debris as a small dot of light with light rays extending from the impact point
The vast plume of dust and debris blasted from the surface of the asteroid Dimorphos by NASA’s DART spacecraft. In this image, the more than 10,000-kilometre long dust trail — the ejecta that has been pushed away by the Sun’s radiation pressure, not unlike the tail of a comet — can be seen stretching from the center to the right-hand edge of the field of view / Credit: CTIO/NOIRLab/SOAR/NSF/AURA/T. Kareta (Lowell Observatory), M. Knight (US Naval Academy)
Images from hubble space telescope and james webb space telescope show the dimorphos asteroid as a small dot of light with light rays of surface debris eminating from the surface
These images, Hubble on the left and Webb on the right, show observations of the Didymos-Dimorphos system several hours after NASA’s Double Asteroid Redirection Test (DART) intentionally impacted the moonlet asteroid. / Credit: Science: NASA, ESA, CSA, Jian-Yang Li (PSI), Cristina Thomas (Northern Arizona University), Ian Wong (NASA-GSFC); image processing: Joseph DePasquale (STScI), Alyssa Pagan (STScI)

The recoil from this eruption of debris is expected to have enhanced the effect of the DART spacecraft’s collision with the asteroid, and mission scientists will switch their focus to investigating the momentum transfer from the fast-moving ship to Dimorphos.

Understanding the unique properties of Dimorphos will inform future planetary defence planning by NASA. Such characteristics may not be common to all asteroids, including ones that may one day be set on a collision course for Earth. These analyses will be further assisted by the LICIACube satellite currently in the vicinity of the impacted asteroid, as well as the European Space Agency’s upcoming Hera mission, which will conduct a larger-scale post-impact survey of the crash aftermath. 

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